Our broad objective is to understand how innate immune activation mediated by the immunoreceptor NKG2D leads to enhanced priming and effector functions of the adaptive immune response. NKG2D recognizes a group of self-molecules that are not expressed on most normal cells but are upregulated on tumor cells and infected cells. This suggests that these self-proteins may function as sentinel molecules on offending cells to mobilize an immune response. Elucidation of this pathway is important because it plays a significant role in the host defense against cancers and viruses. Moreover, insights into the mechanism of enhanced priming of an adaptive immune response will be useful to improve vaccines and immunotherapies. Preliminary experiments indicated that NKG2D is expressed by innate immune cells (antigen presenting cells (including dendritic cells) and NK cells). The hypothesis to be tested is that interaction of NKG2D expressed by innate immune cells (APCs and NK cells) with NKG2D ligands expressed by tumor cells and infected cells leads to enhanced priming of a T cell response. Aim 1 seeks to understand the cellular and molecular requirements to enhance priming and memory formation of T cells in various in vivo systems involving the interaction of NKG2D with its ligands. We will follow up on our finding that tumor vaccines expressing NKG2D ligands significantly enhance priming of T cells specific for tumor antigens. Specifically, we will test our hypothesis that interaction of NKG2D ligands on tumor cells with the NKG2D receptor expressed by APCs and NK cells leads to enhanced cross priming of antigen specific T cells. Aim 2 seeks to discover the functions of NKG2D on antigen presenting cells. We will use various in vitro systems to rigorously test the function of this immunoreceptor on APCs. We hypothesize based on our preliminary data that NKG2D preferentially enhances the ability of these cells to cross present antigen. The goal of Aim 3 is to understand the signaling pathways downstream the NKG2D receptor that are involved in enhanced priming of an adaptive immune response. We will use gene targeted mice that lack the relevant signaling adaptor proteins for the NKG2D receptor (KARAP/DAP12 and DAP10) to identify the molecular signals that need to be provided to the APC or NK cell to enhance cross priming of an efficient adaptive immune response. This may allow us to identify molecular targets to enhance the immunotherapy of cancers and infections. [unreadable] [unreadable] [unreadable]